Study solves mystery of how atoms split during fission


Scientists have solved an 80-year-old mystery of how atoms split during nuclear fission, in a discovery that improves understanding about which atoms can form in star explosions and collisions in space.

Professor Cédric Simenel from The Australian National University (ANU) said the findings – which predicted the mass, charge and energy of each fragment of a split atom – helped to better describe the fission process, which remains poorly understood.

“There is a limit to the mass of the atoms that can form in star explosions and collisions of two dense stars, known as neutron stars – we think this is due to fission which splits the heaviest atoms in two,” said Professor Simenel from the ANU Research School of Physics and Engineering.

“Our findings are a major step towards understanding the fission process to be able to simulate its influence on the abundance of the various atoms in the Universe.”

The research team, led by Dr Guillaume Scamps at the University of Tsukuba in Japan, made the fission discovery by developing numerical codes and running them on supercomputers at the National Computational Infrastructure at ANU and in Japan.

“The fact that fission produces a heavy and a light fragment had been a puzzle until now,” Professor Simenel said.

“We found the heavier fragment of a split atom forms a distinctly pear shape due to the structure of the atom.”

Professor Simenel said the researchers would continue to study the heaviest atoms and the role of fission in forming atoms in the Universe.

“In the long term, this discovery could also potentially help engineers design next-generation nuclear power plants, which promise to be safer and cleaner,” he said. 

“The research for the development of these Generation 4 fission reactors is very active and requires not only a good understanding of the fission process, but also theoretical models like the one we’ve done to predict the mass, charge and energy of fission fragments.”

The study is published in Nature.



Associate Professor Cédric Simenel
Head, Department of Theoretical Physics
Research School of Physics and Engineering
ANU College of Science
M: +61 402 710 744 

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